IMPACTO DE LA HIPERTENSIÓN EN LA REACTIVIDAD DEL BYPASS DE ARTERIA MAMARIA. ROL DEL ÓXIDO NÍTRICO EXTRAENDOTELIAL

MARAÑÓN R,; JOO TURONI C,; PROTO V,; COVIELLO A,; PERAL M

Buenos Aires

Congreso; XIII Congreso Argentino de Hipertrnsón Arterial; 2006

Sociedad Argentina de Hipertrnsón Arterial

IMPACT OF HYPERTENSION IN INTERNAL MAMMARY ARTERY GRAFTS REACTIVITY. ROLE OF EXTRAENDOTHELIAL NITRIC OXIDE Rodrigo Marañón, Claudio Joo Turoni, Víctor Proto, Alfredo Coviello and María Peral de Bruno Dpto. Biomédico (Or. Fisiología) - Facultad de Medicina - Universidad Nacional de Tucumán (UNT) - INSIBIO-CONICET, Centro Modelo de Cardiología. Tucumán, Argentina Internal mammary artery (IMA) used in bypass coronary surgery remains patent for longer periods than other grafts Objective: To compare in IMA grafts from hypertensive (HT) and normotensive (NT) patients 1) the presence of endothelium and its functionality, 2) the degree of vascular compliance and basal tone 3) the reactivity to exogenous vasoconstrictors and 4) the role of stretching in NO-release. Methods: Segments of IMA were connected to a isometric force transducer. Nitrites were measured by Griess reaction by absorbance to 540 nm. Endothelial integrity was evaluated by histological (H&E) and immunohistochemistry examination (monoclonal CD34 antibodies). For immunohistochemistry visualization of nNOS slides were incubated antibody rabbit anti-nNOS. Results: An endothelial dysfunction associated with hypertension was found. IMA rings from HT had an impaired response to passive stretching resulting in a decreased relaxation. All IMA grafts had an increased basal tone demonstrated by relaxation to SNP, however, a lesser response was found in HT. Interestingly, it was demonstrated that NO release was present in IMA grafts, despite an endothelial dysfunction, and that stretching increased this NO release. This effect was inhibited by Ca2+-free media, L-NAME and a specific neuronal NO synthase (nNOS) inhibitor. Furthermore, in smooth muscle cells from stretched IMA presence of nNOS by immunohistochemistry was found. Conclusion: We show the impact of hypertension in IMA grafts producing: 1) increased endothelial dysfunction, 2) reduced vascular compliance 3) increased basal tone and 4) impaired responsiveness to exogenous vasoconstrictors and NO release. A specific role of stretching in extraendothelial NO release was demonstrated, which may have an important role in the outcome of IMA grafts due to the protective actions of NO. Keywords: IMA grafts, hypertension, endothelial dysfunction, vascular reactivity, extra endothelial nitric oxide synthase